1. Field of the Invention
The present invention relates to devices and methods for measuring the concentration of a blood component, in particular, to a device and a method for measuring the concentration of a blood component using perspiration.
2. Description of the Related Art
A method of measuring the concentration of a component in the blood such as blood glucose without collecting blood includes a method of measuring based on the concentration of a component contained in perspiration. For instance, U.S. Pat. No. 5,036,861 and Japanese Laid-Open Patent Publication No. 62-72321 describe such a method and device.
Specifically, as a method of forcibly perspiring, U.S. Pat. No. 5,036,861 discloses a medical agent introducing method, that is, a method of introducing the medical agent to a target area, and Japanese Laid-Open Patent Publication No. 62-72321 discloses a warming method, that is, a method of warming the target area. Japanese Laid-Open Patent Publication No. 62-72321 also describes that the perspiration sugar and the blood glucose are correlated.
However, a change in concentration of the sugar concentration in the perspiration is not necessarily correlated with the change in concentration of the blood glucose value. This is also apparent from the graph showing the correlation of the perspiration sugar and the blood glucose shown in Japanese Laid-Open Patent Publication No. 62-72321.
The inventors performed a measurement of the sugar concentration in the perspiration (referred to as perspiration sugar value) and the sugar concentration in the blood (blood glucose value) of after forced perspiration, and obtained a plurality of samples as shown in FIG. 19 to FIG. 26. FIG. 19 to FIG. 22 show samples of a change in concentration between the perspiration sugar value and the blood glucose value in a case where the perspiration is continuously collected after the perspiration acceleration of one time, and respectively shows samples of the measurement value obtained from different subjects. FIG. 24 to FIG. 26 show samples of a change in concentration of the perspiration sugar value obtained from the perspiration from after 0 minutes from the perspiration acceleration until elapse of five minutes, the perspiration sugar value obtained from the perspiration from after elapse of five minutes to elapse of ten minutes, and the blood glucose value by repeating perspiration acceleration with respect to the same subject, and respectively show samples of the measurement value obtained from different subjects.
The inventors verified the samples shown in FIG. 19 to FIG. 22, and found in particular that the change in concentration thereof is not correlated at the beginning of forced perspiration, and that the concentration of the perspiration sugar value rapidly lowers more greatly in the relevant period than in the period after the beginning.
FIG. 23 is a view showing a sample obtained by performing a measurement of the perspiration sugar value and the blood glucose value after exercise perspiration. Measurement after accumulating the perspiration for ten minutes is repeated three times to obtain such a sample. As shown in FIG. 23, in the exercise perspiration as well, the perspiration sugar value at the beginning of perspiration is at high concentration and the concentration changes differently from the change in blood glucose value, similar to the forced perspiration shown in FIG. 19 to FIG. 22. In other words, it is apparent from FIG. 19 to FIG. 23 that the component concentration in the perspiration at the beginning of perspiration is high concentration compared to the subsequent concentration regardless of the perspiration method.
Furthermore, it is verified from the samples shown in FIG. 24 to FIG. 26 that the opening from the change in concentration of the blood glucose value is greater and the correlation is not as found in the change in concentration of the perspiration sugar value obtained from the perspiration from after 0 minutes immediately after the perspiration acceleration until elapse of five minutes than the change in concentration of the perspiration sugar value obtained from the perspiration from after elapse of five minutes until elapse of ten minutes after the perspiration acceleration.
Therefore, when estimating the sugar concentration in the blood using the sugar concentration in the perspiration, the accuracy of the sugar concentration in the blood lowers particularly if the sugar concentration in the perspiration at the beginning of perspiration is used. Similar problems are found when the blood component is other components other than sugar.